Jacob, Switzerland +beginners question

[jacob23]

Hello All,

my name is Jacob, I currently live in Switzerland and have just made my first step into the world of gamma spectroscopy by completing the basic gear, which is the GS-1100-pro driver and an old Scionix Holland 1.5x2.25 NaI(Tl) scintillation detector. It's very exciting to be here and I see many of you produced amazing results. Hopefully I can learn from your work, and with time make some small contribution to the forum community.

Cheers,
Jacob

P.S. Forgive me for asking questions immediately: I still cannot get my head around the PRA, however I could start the Theremino pretty instantaneously and got some intriguing results off the first time. It seems there is a sharp peak at around 761 keV in my background. Could it be that my detector is contaminated? Could it be Nb95?!? Attached are pictures of background, and a measured Cs137 sample.

[Sesselmann]

Jacob,

Thanks for the introduction and good to see that you are already getting some results with Theremino.

PRA is also simple to use when you know the steps, maybe watching my video will help, https://youtu.be/Mp0QYHiS7lU

As for the extra peak you are seeing, I can't imagine what it might be. You should not be seeing any peak there if you have a pure Cs137 source. Remove the Cs137 source and do a background spectrum to check you don't have any other sources near by. Also try repeating the same in PRA.

Theremino enhances the resolution using fancy convolution algorithms, so you need to concider the risk that it might try to make a peak out of something which is not really a peak.

[jacob23]

Dear Steven,

thank you very much for the quick reply. The video you made is very helpful to start and set everything up. I also loved the idea of making the shielding from PVC-pipes and granulated lead. That's really neat, I will use this approach as well.
The source of the problem with PRA was soundcard-related, there was no sharp peaks visible in the audio input window. My built in card is of very low quality, but after some play, it works now. The PRA also gives me this mysterious peak at 771 keV. If it is Nb95 it should go away in few months, if it is some other problem, then maybe I will need a new detector. Anyhow, I am very excited that the setup works! For the moment I think I will focus on getting a good-quality soundcard and building a proper shield. My main interest is finding traces of radioactivity in food.

Best regards,
Jacob

[jacob23]

The issue is solved, it was a silly mistake. After getting the software to work I calibrated the voltage for the scintillation detector. I found the signal plateau starts at around 650-675V and I set the driver to that value (earlier I used 775V). Now, at 675V the mysterious peak is gone, and the signal quality also got much nicer than earlier, the peaks are much smoother. So it's all working nicely now. :-)

[Sesselmann]

Great its working for you now.

Here is a post about an external sound card. viewtopic.php?f=15&t=117

Steven